Why is my 4L80E shifting weaker?

85toyo · Feb 25, 2014

My old truck would randomly get stuck in 3rd gear when the ignition screwed up. Sometimes I could shake the keys around and it would go back to normal. If that didn't work I resorted to punching it softly. Then I would be forced to pull over and restart the truck if beating on the ignition didn't fix it.

There were a few occasions when I couldn't get it to reset so I would be stuck towing a boat around in 3rd which fawkin blows, especially when you get caught at a red light going uphill. I could put it in 2nd manually but it was still tough to get going with a load.

Overall the bad ignition made the trans do some random **** and it never would act up when I hooked a scanner to it.

Woodson Jones Chevy in Fort Payne ended up fixing it for me.

Edit: Mine was a 4L60E

zukimaster · Feb 25, 2014

Well after reading all this, I would go get me a new switch there buddy, kinda sounds like your problems.

TacomaJD · Feb 25, 2014

yankster said:
When my cigarette lighter fuse is blown my BullyDog tuner won't come on either...

One of my cigarette lighter holes doesn't work (it has 2), so I imagine that is exactly why. I'll try a new fuse and maybe the OBD II port will work, so I can at least see what the code is before I go to buying replacement parts.

Hope I can get it fixed this week, was planning on dropping my rig off at Angryfab Saturday. :driving:

grcthird · Feb 25, 2014

Lots of vehicles use the lighter fuse to power the obd port, so fix that, then get us some codes so we can start properly diagnosing this instead of just suggesting **** to throw at it.

TacomaJD · Feb 25, 2014

TacomaJD said:
I'll try a new fuse and maybe the OBD II port will work, so I can at least see what the code is before I go to buying replacement parts.

grcthird said:
Lots of vehicles use the lighter fuse to power the obd port, so fix that, then get us some codes so we can start properly diagnosing this instead of just suggesting **** to throw at it.

^^^ that's the plan molaugh

Gonna try to fool with it tonight after work.....effing 2nd shift.

onepieceatatime · Feb 26, 2014

I've only got one port in the front of my Chevy that works too but the OBD port is still fine.

ibrokeit · Feb 26, 2014

TacomaJD said:
^^^ that's the plan

Gonna try to fool with it tonight after work.....effing 2nd shift.

Stupid excuse. That just gives ya time before work to mess with it.

muddinmetal · Feb 26, 2014

What's the Vin# punk?

TacomaJD · Feb 27, 2014

Re: Re: Re: Why is my 4L80E shifting weaker?

ibrokeit said:
Stupid excuse. That just gives ya time before work to mess with it.

That would require getting up early....I've heard of people getting up early before, but I'm not so sure I know how to.

muddinmetal said:
What's the Vin# punk?

Text sent, hombré.

Fixed blown cig lighter fuse and obd II port works fine now. Plugged programmer up and this is the only code it gave. I am just now posting this after coming in from outside, so I have not done any research on this code yet.

TacomaJD · Feb 27, 2014

Re:

Did just a little bit of reading on engine codes and I'm sort of confused. By googling U0107 it comes up with an issue related to the Throttle Actuation Control module (TAC). A lot of search results came up involving the TAC, actually....but nothing stating Manifold absolute pressure/baro sensor low input. So by Googling only Manifold absolute pressure/baro sensor low input, it brings up an issue related to the MAP sensor. Less results came up with this, but what did come up stated that the code for that issue was P0107, not the U0107 like seen above in my programmer's diagnosis, which doesn't make sense.

Regardless on both issues, a break in or loose wiring problem at or around a connector somewhere was mentioned often. Fawking wiring issues....fml.

grcthird · Feb 27, 2014

The P0107 code is for the map sensor, the U0107 code is for the throttle body actuator, the programmer software probably has a glitch with which description goes with which code, since the truck computer only "gives out" the code and not the description. (You could "test" this theory by unplugging the map sensor and seeing if it throws the P0107 code.)

Going with the U0107 code:
Lost Communication with Throttle Actuator Control Module
Check the ground wire on the left rear of the engine block, lots of issues with it being broken.
Test for 12 volts on the Pink wire at the Throttle Actuator Control (TAC) module and look for loose terminals. (Back probe it with a paper clip while it is plugged in and ignition is on.)

Basically it is either the throttle body, wiring between it and the computer, or a bad computer. My money is on the ground wire being bad or the throttle body.

TacomaJD · Feb 27, 2014

Re:

So just so we're clear on references here, TAC is the technical term for throttle body?

muddinmetal · Feb 27, 2014

Re:

TacomaJD said:
So just so we're clear on references here, TAC is the technical term for throttle body?

Sure is... I'll be damned, it looks like you have a tb issue. If only someone would have told you that a few days ago :fish:

TacomaJD · Feb 27, 2014

Re:

Maybe it's just a ground or broke wire. I wanna pull my **** down to Angryfab Saturday dammit. Could use a buddy's truck but I don't wanna bring it down there until I know for a fact it ain't gonna cost me an arm and a leg to fix the tow digger. (See what I did there.)

TacomaJD · Mar 1, 2014

Re:

Well been fooling with this thing all day. Here's how it went. I did not see anything around the throttle body plug that looked like a wiring issue. Everything looked good. The big ground coming from back of engine to chassis looked good. So I hooked up my tuner to just clear the code and then proceeded to install my factory backed up tune back in the computer. Went through the steps, completed fine. Turned key off, unplugged tuner, went to start engine to back out of the shop, and sumbitch wouldn't crank. Battery died all the way down where it wouldn't even hardly turn the motor over and I just had crunk the fawker up and pulled it from the driveway into the shop, not long before this.

Ok, so i'm thinking hmm...maybe the battery was about to **** out and the low voltage is what caused it to throw the code. Well battery had 3 year free replacement and it is only 2 years old so I went and got a brand new one. Came home, installed new battery, and started the engine. Started fine, shut the hood, drove about 2 or 3 miles around my neighborhood, and came back home. Worked perfectly, thought I had it fixed....no limp mode, no check engine light.

Went in changed clothes getting ready to go grill out and have a few brews in celebration of a good friend's job promotion, and the motherfucker cranks immediately into limp mode. Cut it off and let it sit a few minutes and started back....right into limp mode. Done this 4 times....all the same result. Kept trying because I would like to move the sumbitch from where it's parked in my yard, but I guess it will have to sit there for the time being.

Where my dad works, has a bunch of junked out GM trucks. We are going to try taking a throttlebody off of one of them and trying it on mine just to troubleshoot. But that will be another day, as grilling out and beer are currently more important.

zukimaster · Mar 1, 2014

I promise you that you will be so much time and money ahead, just to take it to the Chevy store, them guys fool with that stuff everyday, and have the tools to check it! time you take another couple weeks running here and there, and changing this and that part out, you will be money ahead! already been down this road many times.

TacomaJD · Mar 1, 2014

Re: Re: Re: Why is my 4L80E shifting weaker?

zukimaster said:
I promise you that you will be so much time and money ahead, just to take it to the Chevy store, them guys fool with that stuff everyday, and have the tools to check it! time you take another couple weeks running here and there, and changing this and that part out, you will be money ahead! already been down this road many times.

Jakes said his dad could bring the diagnostic tool home from the dealership one day and check it out. The motherfucker won't move right now at all, so I can't get it no where lol. Damn aggravating ****.

KILLERB468 · Mar 2, 2014

also check the wires at the throttle body, they may be connected and look intact. But really the wire broke or pulled away from the connector and only holding on by the casing. light tugs on the wire will help diagnose that, a broken wire the casing will stretch, or you can pin them out with an ohms tester.

muddinmetal · Mar 2, 2014

I am 98% sure you need a throttle body.... the other 2% is split 1% says it could be the connector at the tb & 1% thinks it might be something else.

TacomaJD · Mar 2, 2014

Re: Re: Re: Why is my 4L80E shifting weaker?

KILLERB468 said:
also check the wires at the throttle body, they may be connected and look intact. But really the wire broke or pulled away from the connector and only holding on by the casing. light tugs on the wire will help diagnose that, a broken wire the casing will stretch, or you can pin them out with an ohms tester.

Checked the wires at the TB plug too and everything looks perfect, they all feel tight in the plug when tugging on them. Inspected the pins in TB side female part of the plug and they all are shiny and clean, no oxidization or anything.

Like Tyler said, I bet it's equipment failure. Won't know til we swap it out with another used one and see. My buddy's dad is service manager at a Chevy dealership and said there was a recall on the TB on some of those trucks, he'd have to run the vin to see if mine qualified, but that'd be sweet to get a new one for free! Gonna let him check that out too.